Cosine (cos) Calculator
Cosine (cos) Calculator
Calculated cos() of the number
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cos() function
The cosine of an angle is the ratio of the length of the side adjacent to that angle to the length of the hypotenuse, in a right triangle. On the unit circle, cos(θ) is the x-coordinate of the point where the angle's ray crosses the circle.
This is a free online cos calculator — enter a value above and the cos() result updates automatically.
Important Abbreviations to Remember
- SOH: Opposite / Hypotenuse (Sine)
- CAH: Adjacent / Hypotenuse (Cosine)
- TOA: Opposite / Adjacent (Tangent)
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Understanding the Main Trigonometric Functions
The trigonometric functions — also called circular or goniometric functions — are functions of an angle that relate the angles of a right triangle to the lengths of its sides. They're central to the study of triangles and to modeling periodic phenomena (waves, oscillations, rotation), among many other applications in physics, engineering and geometry.
Every value below is computed from a triangle inscribed in the unit circle — sine and cosine are the vertical and horizontal legs of that triangle, and the other four functions (tangent, secant, cosecant, cotangent) are ratios built from them. Drag the point around the circle to see how each ratio changes with the angle. A handful of angles (0°, 90°, 180°, 270°, 360°) make one of those ratios divide by zero — those are undefined rather than a nonsensical number.
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